Many industrial processes, such as sanding, grinding and milling generate high concentrations of dust particles in the surrounding air. Unchecked inhalation of such particles can damage the lungs of industrial employees breathing such contamined air. In addition, these particles present a fire hazard as well as a health hazard if the materials being processed are combustible in fine dust or powder form. A spark from a sanding belt, grinding wheel or static electricity can trigger explosive spontaneous combustion. Such explosions and fires have occurred in furniture plants and grain mills where high densities of fine sawdust or flour were allowed to contaminate the air.
Clearly a safe, efficient and economical means for cleansing such contaminated air is needed. The problem is not solved by a device which merely exhausts large volumes of the contaminated air from the factory into the outside air; local and national pollution laws prohibit this practice. These laws and other environmental considerations necessitate the use of some sort of filtering process which purifies the air instead of merely spewing it outside. In addition, it is desirable to incorporate some sort of humidity control process into the purification process, so that the relative humidity within the plant or factory is maintained at a comfortable level (40-50%) for the employees. Humidity control is especially desirable in wood working industries such as furniture plants, where a low relative humidity causes expensive wood to dry out and split.